鉴于这些JPA映射

// grandparent
@Entity
@Table(name = "three_phase_motor_input")
public class ThreePhaseMotorInput implements IThreePhaseMotorInput,Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @Version
    private Integer version;

    @OneToOne(orphanRemoval = true,cascade = CascadeType.ALL,optional = true,targetEntity = UnapprovedThreePhaseMotor.class)
    @JoinColumn(name = "unapproved_id")
    private IThreePhaseMotor unapprovedMotor;

// parent
@Entity
@Table(name = "unapproved_three_phase_motor")
public class UnapprovedThreePhaseMotor extends ThreePhaseMotor {
    @OneToMany(orphanRemoval = true,fetch = FetchType.LAZY,targetEntity = UnapprovedThreePhaseWire.class)
    @JoinColumn(name = "motor_id",referencedColumnName = "id",nullable = false)
    @OrderColumn(name = "idx")
    private List<IThreePhaseWire> wires;


// child - Abstract
@Entity
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
@Access(AccessType.FIELD)
public abstract class ThreePhaseWire implements IThreePhaseWire,Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

// child concrete
@Entity
@Table(name = "unapproved_three_phase_wire")
public class UnapprovedThreePhaseWire extends ThreePhaseWire {

将祖父节中的unapprovedMotor设置为null时,日志文件中的sql语句顺序

572353115 UPDATE three_phase_motor_input SET status = ?,version = ?,approved_id = ?,unapproved_id = ? WHERE id = ? AND version = ? [params=(int) 1,(int) 8,(null) null,(long) 896,(int) 7]
 1683522521 DELETE FROM unapproved_three_phase_motor WHERE id = ? AND version = ? [params=(long) 209938,(int) 1]
 446470297 DELETE FROM unapproved_three_phase_wire WHERE id = ? [params=(long) 1394]

这会导致外键约束错误,因为在执行父删除语句时子项仍然存在.